1. Field of the Invention
The method of this invention relates generally to the field of computer aided exploration for hydrocarbons using seismic data of the earth. In particular, the invention concerns a computerized method and apparatus including a programmed computer for identifying valid fault curves on vertical seismic sections of a three dimensional volume of seismic data.
2. Description of Prior Art
Because faulting of stratigraphic subterranean formations creates hydrocarbon traps and flow channels, accurate identification of fault curves and fault surfaces is essential to the interpretation of most seismic data volumes. Explorationists today use an interactive workstation on which is displayed sections of seismic data. A fault surface is characterized by a series of fault curves, each one representing the intersection of a fault surface with a particular vertical seismic section.
With existing workstation tools (e.g., existing interactive computer programs), the interpretation of faults is tedious and limited. For a particular vertical section, the workstation operator must carefully move a cursor over the entire length of an observed fault curve, pausing to click at points along the curve enough times so that connecting the points by straight line segments satisfactorily represents the entire curve. Then, this process must be repeated for each section on which the fault curve is desired, perhaps hundreds of sections.
3. Identification of Objects of the Invention
A primary object of the invention described herein is to provide a method and apparatus for automatically producing a "valid fault curve" on a vertical seismic section from user supplied information of as few as two coordinates of the fault, i.e., coordinates of two points along or near the curve on that section. A valid fault curve is a succession of points distributed along a fault event as identified by the invention, in the seismic data, so that connecting the points consecutively by straight line segments produces a continuous curve, known as a "polyline", describing the fault. The word "valid" is generally used herein to characterize the existence of a fault curve which has been validated by the invention from evidence in the seismic data.
Another object of the invention is to provide a method of automatically translating a valid fault curve from the vertical seismic section to a second seismic section in a three dimensional volume of seismic data.
Still another object of the invention is to provide a method for automatically producing valid fault curves on all desired vertical seismic sections from user supplied information of as few as two coordinates of the fault on just one of the sections.